Control system for a compressor with speed-based subsystem, synthesis plant and control method

Abstract

Control system arranged for a rotary compressor driven by a rotary engine, and includes: a first control subsystem, a second control subsystem and a selector; the first control subsystem is arranged to provide a first control signal as a function of the performance of the compressor; the second control subsystem is arranged to provide a second control signal as a function of the speed of the compressor; the selector is arranged to select the first control signal or the second control signal as a third control signal to be provided to a power control input of the engine.

1 . A control system for a rotary compressor driven by a rotary engine, comprising:
 a first control subsystem comprising:
 a performance input arranged to receive a first measure signal indicating performance of the rotary compressor, and 
 a first control output arranged to provide a first control signal as a function of the first measure signal; 
   a second control subsystem comprising:
 a speed input arranged to receive a second measure signal indicating rotation speed of the rotary compressor or the rotary engine, and 
 a second control output arranged to provide a second control signal as a function of the second measure signal; 
   a selector comprising:
 a first input electrically connected to the first control output, 
 a second input electrically connected to the second control output, and
 a third control output arranged to provide a third control signal to a power control input of the rotary engine, 
 wherein the selector is arranged to select the first control signal or the second control signal as the third control signal to be provided at the third control output. 
 
   
     
     
         2 . The control system of  claim 1 , wherein the selector is arranged to select the second control signal instead of the first control signal at one or more of at least the following conditions:
 the second control signal is higher than the first control signal,   aid second control signal is lower than the first control signal.   
     
     
         3 . The control system of  claim 1 , wherein the second control subsystem comprises a first speed controller of the PID type, only the P term and the I term being used, wherein the first speed controller is arranged to determine a control signal based on the second measure signal and a lower speed limit, and provide it at an output. 
     
     
         4 . The control system of  claim 3 , comprising a first selector arranged to select the control signal at the output of the first speed controller when the second measure signal has a low value. 
     
     
         5 . The control system of  claim 1 , wherein the second control subsystem comprises a second speed controller of the PID type, only the P term and the I term being used, wherein the second speed controller is arranged to determine a control signal based on the second measure signal and an upper speed limit, and provide it at an output. 
     
     
         6 . The control system of  claim 5 , comprising a second selector arranged to select the control signal at the output of the second speed controller when the second measure signal has a high value. 
     
     
         7 . The control system of  claim 1 , wherein the first control subsystem is arranged to calculate a performance error signal as a difference between a performance setpoint and the first measure signal. 
     
     
         8 . The control system of  claim 7 , wherein the first control subsystem comprises a load controller arranged to determine a load demand based on the performance error signal. 
     
     
         9 . The control system of  claim 8 , wherein the first control subsystem comprises a converter arranged to determine a control signal based on the load demand. 
     
     
         10 . The control system of  claim 9 , wherein the converter is a split converter and is arranged to provide alternatively a control signal and an anti-surge control signal. 
     
     
         11 . The control system of  claim 1 , wherein the performance input of the first and/or second subsystem is arranged to receive a measure signal indicating suction pressure of the rotary compressor. 
     
     
         12 . The synthesis plant comprising:
 a rotary compressor comprising an inlet and an outlet, wherein the inlet is arranged to receive a gas mixture;   a rotary engine driving the rotary compressor; and   a control system according to  claim 1 .   
     
     
         13 . The plant of  claim 12 , wherein the rotary engine is a steam turbine. 
     
     
         14 . The plant of  claim 12 , comprising a reformer upstream the rotary compressor, wherein the reformer comprises an outlet fluidly connected to the inlet of the rotary compressor. 
     
     
         15 . A method of controlling a rotary compressor driven by a rotary engine, comprising:
 measuring a parameter of the rotary compressor, the parameter indicating performance of the rotary compressor,   generating a first control signal as a function of the parameter,   measuring a rotation speed of the rotary compressor or the rotary engine,   generating a second control signal as a function of the rotation speed,   generating a third control signal by selecting between the first control signal and the second control signal, and   providing the third control signal to control input terminals of the rotary engine.   
     
     
         16 . The method of  claim 15 , wherein the second control signal is selected instead of the first control signal at one or more of at least the following conditions:
 the second control signal is higher than the first control signal,   the second control signal is lower than the first control signal.